1. Field of the Invention
The present invention relates to an optical recording medium for checking compatibility of an optical pickup device and to a method of checking an optical pickup device using the same. More particularly, the present invention relates to an optical disk for checking whether an optical pickup device is capable of reproducing signals of a plurality of optical disks of different standards, and to a method of checking.
2. Description of the Background Art
An optical disk having the thickness of about 1.2 mm from which signals are read by using a semiconductor laser, such as a CD-ROM (Compact Disk-Read Only Memory) has been proposed. In order to read a signal from this type of optical disk, an objective lens for pickup is controlled in accordance with focus and tracking servo while pit string on a signal recording surface is irradiated with a laser beam.
Recently, density has been made higher to record motion picture for a long period of time. For example, a DVD (Digital Video Disk) standard has been proposed for recording about 5G byte of signals on one surface of an optical disk having the diameter of 12 cm which is the same as an ordinary CD-ROM. The substrate for the DVD is about 0.6 mm in thickness, and by adhering two such disks as one and the other surfaces, it is possible to record about 10G byte of signals in one DVD.
Accordingly, in the future, there will be optical disks having thin substrate of 0.6 mm in thickness and optical disks having standard substrate of 1.2 mm in thickness existing together.
Japanese Patent Laying-Open No. 5-303766 discloses an optical pickup device which is capable of reproducing both the high density optical disk having the thin substrate of 0.6 mm in thickness and the standard density optical disk having the standard substrate of 1.2 mm in thickness.
In the situation where optical disks having the thicknesses of 0.6 mm and 1.2 mm exist together, it is most important that an optical pickup device is capable of reproducing a CD (Compact Disk), a CD-R (Compact Disk-Recordable), a DVD and an MO (Magneto-Optical) disk. Accordingly, an optical pickup device has been developed which is compatible in reproducing 1) CD and DVD, 2) CD-R and DVD, 3) MO disk and DVD, 4) CD, CD-R and DVD, and 5) CD, MO disk and DVD. Therefore, in manufacturing such pickup devices, it is necessary to quickly check whether the optical pickup device has desired compatibility.